Endoscopic Carpal Tunnel Release Via a Biportal Approach

Median nerve compression at the wrist was described by Sir James Paget in 1853, but it was not until 1933 that Learmonth first described a surgical procedure to release the compressed nerve at the wrist. First popularized by Phalen in the 1950s, open and direct transection of the transverse carpal ligament has become the standard surgical technique for surgical treatment of carpal tunnel syndrome. Okutsu in 1986 was the first to perform and report on the release of the transverse carpal ligament (TCL) in patients with carpal tunnel syndrome using an endoscopic technique. Since the introduction of endoscopic carpal tunnel release, several authors have championed different endoscopic techniques to release the entrapped median nerve. Overall, endoscopic approaches are generally divided into two categories based on the number of incisions made to introduce the endoscopic instrumentation. Single-portal techniques include those developed by Okutsu, Menon, and Agee. Double-portal techniques include procedures introduced by Chow, Resnick and Miller, and lastly Brown. Presented in this chapter is the two-portal technique as described by Brown.

60.2 Patient Selection

Endoscopic release of the transverse carpal ligament (TCL) should be reserved for patients with classic signs and symptoms of idiopathic carpal tunnel syndrome. This category accounts for ~ 43% of carpal tunnel syndrome cases. Symptoms may include a dull ache and pain or discomfort of the hand, forearm, or upper arm; hand paresthesia; weakness of the hand; and nocturnal paresthesias relieved with shaking of the hand. Provocative factors inducing these findings include sustained hand or arm position and repetitive action of the hand or wrist. Physical examination may be normal, but many patients have positive Phalen’s or Tinel’s sign, thenar musculature weakness or atrophy, and sensory loss in the distribution of the median nerve. The patient for whom an adequate trial of conservative therapy fails to effect improvement and who has positive electrodiagnostic studies becomes a candidate for endoscopic release of TCL. Systemic cause of carpal tunnel syndrome, such as acromegaly, thyroid disease, pregnancy, and proliferative tenosynovitis, must be ruled out before considering endoscopic carpal tunnel release.

Several conditions preclude dissection of the TCL with the endoscopic technique. Contraindications include a history of open carpal tunnel release and patients with proliferative tenosynovitis or concomitant ulnar nerve entrapment. Patients with mass lesions (e.g., neuromas) should not undergo endoscopic operation. Patients with a history of previous trauma or anatomical anomalies should be excluded as well. I have found that performing endoscopic carpal tunnel release on large men with bulky hands can present a significant challenge.

60.3 Preoperative Preparation

Anesthetic management of patients undergoing endoscopic carpal tunnel release can be local, regional, or general. Many surgeons advocate the use of local or regional anesthesia (Bier block). My preferred method is rapid mask general anesthesia. This is quickly and easily done using propofol and does not require endotracheal intubation. After placement of an intravenous line, a bolus of propofol is given at 1 mg/kg, followed by continuous infusion of 100 mg/kg/h. Induction is immediate, as is its reversal. Generally, the procedure lasts between 5 and 10 minutes. Using this method, the patient is totally pain free during the procedure and amnestic for the event. Patients are discharged 1 to 2 hours after the procedure and full recovery from anesthesia; however, patients with history of esophageal reflux or with other complicating factors should be operated upon using regional or endotracheal general anesthesia.

60.4 Operative Procedure

60.4.1 Positioning

With the patient in the supine position, the affected arm is placed extended on a hand table or an arm board, and a tourniquet is placed above the elbow. The hand and forearm are prepared with povidone iodine scrub and paint, followed by standard draping and impermeable and split sheets. It is important that the surgeon’s dominant hand be situated closest to the patient, and this will vary with patient’s affected hand and side of surgeon’s dominance ( ▶ Fig. 60.1, ▶ Fig. 60.2, ▶ Fig. 60.3, ▶ Fig. 60.4). The television monitors should be placed directly across from the surgeon as well as the assistant ( ▶ Fig. 60.5).

Fig. 60.1 Operating room setup for a right-handed surgeon operating on a patient’s right hand.

Fig. 60.2 Setup for a right-handed surgeon operating on a patient’s left hand.

Fig. 60.3 Setup for a left-handed surgeon operating on a patient’s right hand.

Fig. 60.4 Setup for a left-handed surgeon operating on a patient’s left hand.

Fig. 60.5 Final room setup allows both the surgeon and assistant to sit across each other and yet have the ability to visualize the surgical field directly across from each on a television monitor. The surgical technician is situated at the end of the hand table.

60.4.2 Instrumentation

The equipment necessary to perform this procedure is found in all modern hospitals: television monitors, a rigid 4-mm, 30-degree endoscope with light source, and a mounted camera. The specific endoscopic instruments (Endotrac System) are manufactured by Instratek (Houston, TX) and consist of ergonomically well designed obturator-cannula complex for entering the carpal tunnel and disposable hook knife ( ▶ Fig. 60.6). Although the equipment is sold as a set or separately, the entire procedure can be performed with only three instruments: a synovial elevator, an obturator, and a hook knife. Other instruments available include raspers, probes, and retractors. The synovial elevator is used to ascertain the appropriate plane of dissection as well as to remove synovium from the undersurface of the TCL. The obturator consists of a rigid 4-mm tapered rod encased in a removable slotted cannula. Once inserted, the open end of the cannula should lie against the undersurface of the TCL. After insertion of the endoscope, the 30-degree angle lens will afford an excellent view of the TCL. Several types of blades and knives are available to section the ligament. Manufacturers make hook, forward, and triangular blades. The only other instruments needed to perform this procedure are a ruler, a marking pen, a single-toothed Adson’s forceps (Codman, Raynham, Massachusetts), and tenotomy scissors.

Fig. 60.6 Endotrac system instruments: (a) synovial elevator used for removing synovium from the undersurface of the transverse carpal ligament, (b) an obturator with is inserted inside, (c) an open-ended cannula, (d) a right-angled probe, and (e) a handle into which a disposable hook blade is attached.

60.4.3 Anatomical Landmarks

Complete familiarity with anatomical landmarks of the median nerve and associated structures of the carpal tunnel is essential for a safe and excellent outcome. Several superficial landmarks can assist the surgeon and adequately plan the surgical approach. Kaplan’s cardinal line extends along the base of the extended thumb and runs parallel to the distal palmar crease. A line can be drawn perpendicular to the distal wrist crease and located along the ulnar side of the fourth digit. The intersection of these two lines indicates the location of the hook of the hamate, or the most ulnar extent of the TCL ( ▶ Fig. 60.7). Kaplan’s line approximates the most distant edge of the TCL, which blends proximally, at the distal wrist crease with an antebrachial fascia ( ▶ Fig. 60.8). The median nerve is located on the radial aspect of the carpal tunnel and radial to the palmaris longus tendon. The ulnar nerve enters the palm on the ulnar aspect of the hook of the hamate and into the Guyon’s canal. The palmar arterial arch is located 1 to 2 cm distal to the edge of the TCL. Therefore, there is a small anatomical corridor devoid of major neurovascular structures, where the TCL can be safely sectioned using endoscopic techniques ( ▶ Fig. 60.9).

Fig. 60.7 External landmarks: Kaplan’s cardinal line (dotted line A) is seen extending parallel to the distal palmar crease and along the base of the extended thumb. A second line drawn along the ulnar aspect of the fourth digit (dotted line B) will intersect Kaplan’s line and indicates the location of the hook and the hamate (darkened oval).

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